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This patch was triggered by a remark from Russell that
introducing a call to the waituart (needed to fix debug prints
on the Qualcomm platforms) was dangerous because in some cases
this will involve waiting for a modem CTS (clear to send)
signal, and debug messages would maybe not work on platforms
with no modem connected to the UART port: they will just
hang waiting for the modem to assert CTS and this might never
happen.
Looking through all UART debug drivers implementing the waituart
macro I discovered that all users except two actually use this
macro to check if the UART is ready for TX, let's call this
TXRDY.
Only two debug UART drivers actually check for CTS:
- arch/arm/include/debug/8250.S
- arch/arm/include/debug/tegra.S
The former is very significant since the 8250 is possibly
the most common UART on the planet.
We have the following problem: the semantics of waituart are
ambiguous making it dangerous to introduce the macro to debug
code fixing debug prints for Qualcomm. To start to pry this
problem apart, this patch does the following:
- Convert all debug UART drivers to define two macros:
- waituartcts with the clear semantic to wait for CTS
to be asserted
- waituarttxrdy with the clear semantic to wait for the TX
capability of the UART to be ready
- When doing this take care to assign the right function to
each drivers macro, so they now do exactly the above.
- Update the three sites in the kernel invoking the waituart
macro to call waituartcts/waituarttxrdy in sequence, so that
the functional impact on the kernel should be zero.
After this we can start to change the code sites using this
code to do the right thing.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Enable ARM big-endian mode on mach-imx. This requires adding some
byte swapping in the debug functions (which otherwise hang forever)
and of course the secondary core bringup.
Tested (on top of 4.4) on i.MX6 HummingBoard quad-core (IMX6Q).
The patch is pretty much as suggested by Arnd Bergmann, thanks!
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
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Extend imx6q DEBUG_LL uart port selection support to cover all i.MX
SoCs. The 'range' of the Kconfig option gets dropped, as users
looking at the option must know the uart number on his board. The
bottom line is that the build system will report an error if an
invalid port number is picked for given SoC.
The header arch/arm/include/debug/imx-uart.h is created to accommodate
all the uart base addresses. And the header will also be used for
other low-level debug facility later.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
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Only mx508 based board is mach-mx50_rdp and it has been marked as BROKEN
for several releases.
mx508 currently lacks clock support.
In case someone needs to add mx508 support back, then the recommended approach
is to use device tree.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
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imx6q gets 5 uart ports in total. Different board design may choose
different port as debug uart. For example, imx6q-sabresd uses UART1,
imx6q-sabrelite uses UART2 and imx6q-arm2 uses UART4. Rather than
bloating DEBUG_LL choice list with all these uart ports, the patch
introduces DEBUG_IMX6Q_UART_PORT for users to input uart port number
when DEBUG_IMX6Q_UART is selected inside DEBUG_LL choice.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
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Move imx debug-macro.S over to common debug macro directory. It
removes the inclusion to hardware.h by hard-coding the physical
address of uart port and copying IMX_IO_P2V from hardware.h.
Since we will need a common solution, which might use a fixed virtual
address for uart port across platforms, we make a copy of IMX_IO_P2V
here as a temporary solution to enable low-level debug for imx
multi-platform build.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
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